how important is the phase inverter tube for the overall sound?

Discussion in 'Glowing Bottle Tube Amp Forum' started by braveheart, Jun 16, 2019.

  1. braveheart

    braveheart Tele-Meister

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    at the end of the 80s/beginning 90ies many "rack guys" gave up their preamp + poweramp combination, because they realized a normal tube amp sounds "better".

    Does the (missing )phase inverter tube have something to do with it?
     
  2. tubelectron

    tubelectron Tele-Meister

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    Well, I'd say "not more not less" influence than the rest of the amp...

    But that's true : I remember playing on stage with a guitarist who had an amazing rack of amps and FX's (it was the era of the Digitech, the GSP rack multi-Fx units), having only my late 70's Fender Deluxe Reverb SF.

    He had an array of wonderful tones, but I had the tone expected.

    A+!
     
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  3. Dacious

    Dacious Poster Extraordinaire

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    These poweramps do have a phase inverter. You have to have one to split the signal to feed to the two sides of an AB poweramp. So the Mesa 20/20 and Marshall 50/50 are two 20 watt and 50 watt amps respectively. They have a pair of tubes each with phase inverter and output transformer.

    If you don't have a phase inverter tube, you can use a transformer like the Musicmaster Bass amp. But you need a phase inverter.
     
  4. kbold

    kbold Tele-Meister Silver Supporter

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    Some overlook the PI tubes effect.
    Do some tube rolling, and you'll find the PI has as much an influence on both clean and overdriven sound as the input tube.
     
  5. radiocaster

    radiocaster Poster Extraordinaire

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    Change of tastes in popular music. You might want to check out a forum that has nothing to do with gear.
     
  6. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

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    I’m opening a huge can of worms here, but I’ve spent some time with PPIMV Marshalls, and they get that “power tube crunch” at volume levels way too low for the power tubes to be even remotely pushed hard. I think that the phase inverter tube is a huge factor in that crunch sound.
     
  7. Greg_L

    Greg_L Tele-Holic

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    Yup, me too. They actually get dirtier IMO with the PPIMV turned down a little. I'm not exactly sure why, but it happens. The presence control goes out the window, I'm assuming the negative feedback loop has collapsed, and things get raunchy....in a good way.
     
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  8. bftfender

    bftfender Friend of Leo's

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    just bring chan vol down to balance out the xtra gain..it 100% works..yes the amp compresses more with PPIMV but easily compensated with the chan volumes. I play em all day every day & they are the easiest amps for vol changes..just move the chan volumes,,,bring master up to clean it..ask a good amp tech..MV are to be use from level down ..not zero up
     
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  9. Greg_L

    Greg_L Tele-Holic

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    Yes, thanks, I think I got it figured out. You're not the only one here with big loud Marshalls. :cool:;)
     
  10. bftfender

    bftfender Friend of Leo's

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    which further can be adjusted with guitar vol knob
     
  11. bftfender

    bftfender Friend of Leo's

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    [delete
     
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  12. JD0x0

    JD0x0 Poster Extraordinaire

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    The imbalances in a Phase inverter can change clipping characteristics, and a clipping phase inverter has different characteristics than your typical triode gain stage does, as well.

    A tube PI and power amp also respond differently than a class A/B solid state output amp. There's generally no voltage sag in SS power amps. Class A/B guitar amps tend to have quite a bit of voltage sag in comparison, even with solid state rectifiers.
     
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  13. Les Paul lover

    Les Paul lover Tele-Meister

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    All I can say is that changing PI valves from any of JJ, EH, nos RFT or Tungsram d8dnt change the sound of the amp i put them in.
     
  14. jimash

    jimash Friend of Leo's

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    I can get a certain amount of mileage out of switching from a 12 ax7 to a 12 at7. Or Vice versa. Would a 12au7 work in a 20 watt amp w. el84's ?
     
  15. Dacious

    Dacious Poster Extraordinaire

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    It would work and it's a driver tube which will take the current - but you may lose a lot of gain, more than is desirable. Possible big volume drop. It doesn't hurt to try but be prepared for disappointment.
     
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  16. MuddyWolf

    MuddyWolf Tele-Meister

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    I used to ignore the PI tube as an afterthought. Now i see it as the second most important pre tube after v1. But all 3 should be regarded important. If you ride a 3 wheel motorcycle which wheel are you willing to do without?
     
  17. Greg_L

    Greg_L Tele-Holic

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    The front wheel. I'll just ride wheelies everywhere.
     
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  18. Mike Eskimo

    Mike Eskimo Doctor of Teleocity Ad Free Member

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    All I know is not much.

    But contained within that “not much” is the fact that I stuck a trash-picked Telefunken ECC81 in the V3 spot in my AC15C1 and it smoothed it out/made it less harsh-sounding .

    Just plain sounded better.

    I took that little valve outta there when I sold the back-breaker because it was breaking my back , as you’d expect.

    Bye
     
  19. Paul in Colorado

    Paul in Colorado Telefied Ad Free Member

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    Unless it was one of those bikes with two wheels in the front with the power going to the single rear wheel. :D
     
  20. Greg_L

    Greg_L Tele-Holic

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    Then I'd lose one of the front wheels and just lean real hard to one side.
     
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